With renewed interest in Stirling engines, there has been an ever increasing attempt to improve its efficiency and reduce the cost of fabrication to that of more conventional engines, so as to produce a competitive, cost effective product. One of the important requirements for efficient operation of a Stirling engine is an efficient utilization of the thermal energy which is generated by the combustion gas and conveyed to the working fluid. (See for example "Stirling Engines" by G. Walker, 1980 Oxford University Press, for background information). There have been many engines which are directed towards improving this. See for example U.S. patent applications, Ser. No. 423,625 for an "Internal Heater/Cylinder Head for a Stirling Engine" and Ser. No. 423,528 for an "Internal Finned Heater and Cooler for Stirling Engines", and the patents referred to therein.
While certain heater head assemblies have proven satisfactory, it has become desirable, particularly in free piston Stirling engines, to provide an improved low-cost head which is relatively easy to fabricate yet provides high performance. In this regard, a monolithic cast structure having fins cast with the pressure vessel is preferred. However, to provide adequate heat transfer, such an assembly must be fabricated with fine enough dimensions to provide efficient thermal transfer. Unfortunately, heretofore, the heater heads in this regard have either been too complex to cast effectively or lacked sufficient performance levels.
In addition, it is necessary that such a structure must be capable of withstanding high pressure and thermal loading safely without excessive thermal energy loss to adjacently positioned elements of the engine.